Closing sockets and discarding queued data (UNIX domain)

Chapter 8, Interprocess communication using UNIX domain sockets

When a socket is no longer of use, the process can discard it by calling close(S):

   close(s);

If data is associated with a socket which promises reliable delivery (a stream socket), the system continues to attempt to transfer the data. Data undelivered after a long period of time is discarded. A client process can cause all data queued for transfer to be discarded immediately by calling shutdown(SSC) on the socket before closing it:

shutdown(s, how);

where how is one of:

0: if the user no longer wishes to read data
1: if no more data will be sent
2: if no data is to be sent or received.